1. Field of the Invention
The present invention generally relates to a standalone input device or keyboard with a planar top surface with no openings or cracks. The input device or keyboard will be used with a personal computer (PC), control panels for operating equipment, and for data input in rugged environments where an internal light beam is emitted out through an optical opening into bright sunlight ambient or total darkness. When a finger is present, the finger encompasses or otherwise covers the opening, thereby substantially blocking out the ambient light from being detected by an internal detector. When the emitter is turned on, the emitted beam is reflected off the finger to the detector which will indicate that a finger is present.
2. Description of the Prior Art
Optical keyboards sometimes use techniques to reduce the ambient lighting effect on finger detection. However, these optical keyboards when used in bright sunlight where bright sunlight saturates the photodiodes do not perform well. Nothing stops the light saturation of the intense ambient lighting in bright sunlight unless, for example, the user moves to a location under an awning or the like. Similarly, in total darkness where the user cannot see the key indicia, these prior optical keyboards fail to perform well. In addition, these prior optical keyboards lack a planer top surface, which is required for cleaning and other purposes in industrial, atomic and medical environments.
U.S. Pat. No. 6,175,679 Veligdan et al shows a keyboard with stacked waveguides to detect a finger.
U.S. Pat. No. 4,629,884 Bergstom shows the use of a radiation propagating prism to detect a finger.
U.S. Pat. No. 4,701,747 Isherwood shows a keyboard where a light beam from a LED reflects to a photodiode when a finger is present, and includes a noise and ambient light rejection circuitry. Unfortunately, Isherwood does not have a design that can accommodate one piece construction and would therefore be unsuitable in environments where nuclear or microbial contaminants could fit in the edges of the various pieces used to make the keyboards. Also, the circuitry for ambient rejection in Isherwood is not conducive to use in bright sunlight.
U.S. Pat. Nos. 5,378,069, 5,577,848, 5,605,406, 5,707,160, and 5,785,439 all to Bowen shows keyboards that detect an users finger by blocking an X and Y optical beam.